1. Field of the Invention
The present invention relates to wireless sensor network (WSN) protocols, and particularly to a coverage, connectivity and communication (C3) protocol method for wireless sensor networks.
2. Description of the Related Art
In ubiquitous and pervasive systems, the lower layer consists of wireless ad hoc and sensor networks. However, the use of wireless sensor networks (WSNs) is becoming more popular. Efficient use of energy is a key issue in WSNs due to very limited battery power. A sensor node that exhausts its battery dies and disconnects from the network, reducing the lifetime of a network. Most of the sensors' energy is consumed in data transmission, and idle listening. Therefore, efficient use of energy can be ensured by improved topology control, duty-cycling, communication protocols, and aggregation and compression of data.
Nodes in WSNs may be in either sleep mode or active mode. A node must be in active mode before it can receive or transmit a message. It is important to note that the sleep mode usually consumes three orders of magnitude less energy, while energy costs for receive and transmit are of the same magnitude. The energy costs for idle listening, receiving, and overhearing are almost similar (within 20-30%). For example, the CC2420 chip consumes only 60 μW in sleep mode, 59 mW while receiving, and 52 mW while transmitting. Therefore, it is best to keep the sensor radio in sleep mode when inactive. In other words, we can conserve energy by minimizing the number of transmissions and by putting the sensor nodes to sleep mode if they are redundant or have no data to send or receive. Therefore, the issues of coverage, connectivity and communication are of primary concern in WSNs. As WSNs are usually overdeployed, it is useful to keep redundant nodes in sleep mode until some neighboring node fails or exhausts its energy. However, identification of the redundant nodes should be done very carefully so that coverage and connectivity of the network is preserved.
While coverage is the ratio of area-sensing covered by the sensors to the total deployment area of the network, connectivity is the availability of a path between each node of the network. Some applications need partial coverage, whereas others need k-coverage. Similarly, some applications need simple connectivity, while others need k-connected network for fault tolerance, infrastructure creation, and maintenance, which consumes a lot of energy in WSNs. Therefore, energy-efficient algorithms are needed for coverage, connectivity and communication in WSNs.
Thus, a coverage, connectivity and communication (C3) protocol method for wireless sensor networks solving the aforementioned problems is desired.